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Date and Time 2017-04-11 15:00 - 16:00
Venue Seminar Room A7F
Speaker Go Shioi
Affiliation Genetic Engineering Team, Division of Bio-Function Dynamics Imaging, RIKEN Center for Life Science Technologies
Title [QBiC-CDB Joint Seminar] Global cell rearrangement during anterior-posterior axis formation in pregastrula mouse embryo
Poster click here to download(PDF)
Host Tatsuo Shibata
Summary After implantation, the embryonic portion of a mouse embryo consists of two monolayer sheets, the epiblast and the visceral endoderm, in a cup-shape structure. The embryos are radially symmetric, with the distal-proximal axis. Cell thickening occurs in the distal visceral endoderm (DVE) at E5.5. The DVE cells express a unique set of genes (AVE genes) encoding transcriptional factors such as Otx2 and Hhex, and signaling antagonists such as Dkk1, Cerl and Lefty1. The expression of AVE genes shifts to the anterior visceral endoderm (AVE) by E6.0, and then the anterior-posterior axis is formed. The shift of the AVE gene expression from DVE to AVE is not due to a change in the cells that express these genes, but due to the movement of the DVE cells. However, it is only DVE cells or part of the visceral endoderm cells that have been analyzed in previous studies. It has remained unclear how other visceral endoderm cells respond to or influence DVE cell movement.
Here we have analyzed the behavior of each visceral endoderm cell with R26-H2B-EGFP mouse line that ubiquitously expresses EGFP in the nucleus. Our analyses demonstrated a global, collective cell rearrangement in embryonic visceral endoderm to form AVE. We have also examined the rearrangement with R26-PHA7-EGFP mouse line that marks the zona adherence. The analyses revealed that the constriction of apical surface of prospective anterior portion of DVE is associated with the initiation of DVE movement. When DVE cells reached the prospective anterior region, their apical size gradually expanded to the lateral region. These results suggest that the change in their apical size is a driving force of the global cell rearrangement in the visceral endoderm. Our study gives new insights on the mechanism of anterior-posterior axis formation.
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